JP2003501335A - High surface area and high activity stable silica sol - Google Patents

Abstract

SUMMARY A stable aqueous colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50 is disclosed. These colloidal silicas do not require treatment with a surface treatment such as aluminum to achieve stability. These aqueous colloidal silica sols can be manufactured and stored at a SiO ₂ solids concentration of 7% by weight or more, and can even have a solids content of 15% by weight or more, at room temperature. It remains stable for more than 30 days. These colloidal silica sols are useful as drainage and retention agents in the papermaking process. Also disclosed is a method for preparing the aqueous colloidal silica of the present invention, and a papermaking process using such a colloidal silica sol.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates to colloidal silica sols having high surface area and improved stability. The invention also relates to a method for producing such a colloidal silica sol and the use of such a colloidal silica sol in paper production. The colloidal silica sol of the present invention is unique because it exhibits this high surface area stability even if it is not surface-modified with, for example, aluminum. Also, the colloidal silica sol of the present invention exhibits such improved stability at a relatively high solids content. Furthermore, the colloidal silica sol of the present invention is advantageous because it exhibits excellent activity in the papermaking process not only in alkaline paper stock but also in acidic paper stock. The colloidal silica sol of the present invention is also useful in other areas of the paper industry, for example, as an accelerator for retention and dehydration.

US Pat. Nos. 5,643,414 and 5,368,833 disclose high surface area colloidal silica microparticles, eg, 700 m ² / g or greater surface area and 2
Those with S-values from 0 to 40 have been described and are useful in papermaking. These patents teach the need to surface treat the colloidal silica particles with aluminum to stabilize the surface area and thus the product. Also US Pat. No. 6,603
No. 805, which has a surface area of 700 m ² / g or less and an S-value of 20 to 40, can be used for producing paper. This patent clearly teaches that a stable colloidal silica product useful for papermaking applications requires a surface area of 700 m ² / g or less in order to be obtained without an aluminum surface treatment. There is.

In contrast, the present invention is useful for papermaking applications and is a stable colloidal silica composition having a surface area of 700 m ² / g or more and an S-value of 20 to 50. I will provide a. Contrary to the teaching of the above patent, the present invention provides colloidal silica that can remain stable without the addition of aluminum to the surface,
It is advantageous.

SUMMARY OF THE INVENTION The present invention has a surface area of 700 m ² / g or more, preferably 750 m ² / g or more, most preferably 800 m ² / g or more and is 20 to 50, preferably 20 to 40.
Stable colloidal silica having an S-value of The colloidal silica of the present invention does not require surface treatment with surface treatment agents such as aluminum to obtain stability.

In the present text, stable colloidal silica means that the surface area of the concentrate is 700 m ² / g or more even when the concentrate is aged at room temperature for 30 days or more, preferably 60 days or more,
And its S-value is defined to remain in the range 20-50. Colloidal silica aqueous sol of the present invention, SiO ₂ solids to produce a concentration of 7 wt% or more, it is possible to store, also possible to SiO ₂ solid content is 15 wt% or even higher concentrations In comparison with the conventional silica aqueous sol, it remains stable at room temperature for 30 days or longer, typically 60 days or longer. Furthermore, the colloidal silica sol of the present invention exhibits improved performance, which is advantageous over conventional colloidal silica sols, when used in a papermaking process or the like. For example, the colloidal silica sol of the present invention made only of silica showed not only high activity in alkaline paper stock, but surprisingly also in acidic paper stock in the papermaking process.

The present invention also provides a method for preparing the colloidal silica of the present invention having a surface area of 700 m ² / g or more and an S-value of 20 to 50. One method is: (a) water, an alkali metal silicate having a molar ratio of SiO ₂ to alkali metal oxide in the range of 15: 1 to 1: 1 and a pH of 10 or more; , A salt corresponding to the acid), and an initial composition (or heel) containing an alkali metal silicate salt and an acid initially present in a weight ratio of 63: 1 or more. Temperature of 100 ° F or less, preferably 85 ° F or less, typically 60 to 85
Maintained below ° F; (b) the starting composition typically has a SiO ₂ content of 5.0 to 7
． 2% by weight, preferably 6.0 to 6.8% by weight and at a temperature below 100 ° F,
Aqueous silicic acid composition, typically maintained at 60 to 85 ° F. or lower, is added slowly and continuously from one-half to three-quarters of the silicic acid composition; The composition is slowly warmed, eg, 115-12 over about 10-35 minutes.
Raise to 5 ° F and maintain that temperature until the addition of the silicic acid composition is complete; (d) optionally, raise the temperature of the composition to 125 ° F or less, typically 115-125.
Maintained at ° F for about 1 hour; (e) then stop heating and optionally water from the resulting composition, with solids content of 7 wt% or more, based on SiO ₂ , typically Remove until it is 11% by weight or more. Also, another method for preparing the aqueous colloidal silica sol of the present invention requires the use of a cation exchange resin to initiate the reaction of the alkali metal silicate salt (see Example 3 below). ). The reaction includes the rate at which the alkali metal silicate is added to the cation exchange resin during polymerization to produce colloidal silica (eg, 0 to 30 minutes, typically 15 minutes or less), and , It is adjusted by the ratio of addition. The molar ratio of the hydrogen ion in the cation exchange resin to the alkali metal ion in the alkali metal silicate is 40 to 1
The range is 00%, preferably 50 to 100%. The temperature during the formation of the colloidal silica in this alternative embodiment of the invention is generally 50 to 100 ° F.
And preferably in the range of 70 to 90 ° F. In this aspect of the method of the present invention, the heat treatment (ie post-treatment) of the colloidal silica product is optional.

DETAILED DESCRIPTION OF THE INVENTION The present invention has a surface area of 700 m ² / g or more, preferably 750 m ² / g or more according to the Sears method (see Anal. Chem., 28, 1981 (1956)). The most preferable value is 800 m ² / g or more, and the S-value (Iler and Dalton, J. Phys. Chem.
, 60, 955 (1956)) is 50, preferably 20 to 50, most preferably 2
Provided is a method for producing colloidal silica having a solid content of 0 to 40 and a solid content of 7 to 20% silica (that is, SiO ₂ ).

One method consists of preparing a starting composition (heel) and subsequent addition of an active silica source (usually in the form of silicic acid or polysilicic acid) over a period of time. During the addition of activated silica, the reaction temperature is adjusted within a given reaction temperature profile. Once a predetermined amount of activated silica has been added, the mixture can be concentrated. The concentration step can be performed by various methods. Such methods may include, but are not limited to, evaporation and / or membrane separation techniques such as ultrafiltration and microfiltration. Water is removed until the final product contains 7 to 20% by weight of SiO ₂ .

In the above method, the starting heel consists of a predetermined proportion of water, any of a number of commercially available silicates or alkaline water glasses, and an acid and / or a salt corresponding to that acid. It was found that the order of addition is not critical, but the acid should be added to the dilution water prior to adding the silicate to facilitate production. The alkaline water glass or silicate can be any conventional material. These are generally potassium or sodium salts. S for Na ₂ O or K ₂ O
The molar ratio of iO ₂ can range from 15: 1 to 1: 1 and is preferably 2.
It should be within the range of 5: 1 to 3.9: 1. Such a water glass solution typically has a pH of 10 or more, particularly pH 11 or more.

The acid used in the above method may be any organic or inorganic acid. Specific examples of such acids include, but are not limited to, mineral acids such as hydrochloric acid, phosphoric acid, sulfuric acid, and materials such as carbon dioxide. Organic acids include acetic acid, formic acid,
Examples include, but are not limited to, propionic acid and the like. Specific examples of suitable salts include sodium sulfate, sodium acetate, potassium sulfate, potassium acetate,
Examples include trisodium phosphate and sodium monohydrogen phosphate.

Once the heel is prepared by the above method, the temperature of the composition is lowered to below 85 ° F., typically below 80 ° F., and usually in the range of 60 to 85 ° F.
In this regard, silicic acid or polysilicic acid is added slowly to the composition, for example, over a total duration of about 4 hours. The silicic acid suitable for the present invention can be prepared by a conventionally known method such as cation exchange of the above-mentioned diluted solution of alkali water glass. Typically, the dilute solution contains 3 to 9 wt% solids based on SiO _2.
In particular, it is contained in an amount of 5.0 to 7.2% by weight, preferably 6.0 to 6.8% by weight. Representative commercial preparations are US Pat. Nos. 3,582,502 and 2,24.
4, 335, the disclosures of which are incorporated by reference. The weight ratio of alkali metal silicate to acid can vary and is typically greater than 63: 1. About one-half to three-quarters of silicic acid or polysilicic acid,
The composition is added slowly and continuously into the composition with agitation, while maintaining the temperature of the composition below 85 ° F, typically about 60-85 ° F. Then, the temperature of the composition is slowly raised, for example, 1 to 10 to 35 minutes.
The temperature is raised to 15 to 125 ° F. and this temperature range is maintained until the balance of silicic acid or polysilicic acid is added to the composition. Then, if necessary, the temperature of the composition is increased to 12
Maintain below 5 ° F, typically 115-125 ° F for about 1 hour. If desired, water can then be removed from the composition by known procedures until the solids content of the composition is greater than or equal to 7% by weight, typically greater than or equal to 11% by weight.

Another method for preparing the aqueous silica sol of the present invention is described below. This method requires the use of a cation exchange resin, preferably a weak acid cation exchange resin, to initiate the reaction of the alkali metal silicate (see Example 3 below) to produce colloidal silica. To do. This reaction depends on the rate at which the alkali metal silicate is added to the cation exchange resin during the polymerization to produce colloidal silica.
And, it is adjusted by the ratio of addition. The heat treatment of the colloidal silica product is
This aspect of the method of the invention is optional.

This another method for preparing the stable colloidal silica sol of the present invention comprises (a) a reaction vessel having an ion exchange capacity in hydrogen form of 40% or more, preferably 50%.
The reaction vessel is filled with the above cation exchange resin, and the reaction vessel is provided with means for separating colloidal silica formed during the process from the ion exchange resin, for example, means comprising a screen provided near the bottom of the reaction vessel. (B) Aqueous alkali metal silicate having a molar ratio of SiO ₂ to alkali metal oxide of 15: 1 to 1: 1 and a pH of 10.0 or more, preferably 11 or more, in the reaction vessel. Filling with salt (essentially all at once); (c) the contents of the reactor with a pH of 8.5 to 11.0, preferably 9.2 to 10. Stir until it reaches a range of 0; (d) Add the alkali metal silicate and add p of the contents of the reaction vessel.
H is adjusted to 10.0 or more, preferably 10.4 to 10.7; (e) The produced colloidal silica is separated from the ion exchange resin and taken out from the reaction tank. The pH adjustment in the step (d) may be carried out in the reaction tank or after removing the obtained colloidal silica from the reaction tank. This pH adjustment is typically done within 10 minutes to 3 hours after the end of step (e).

It was found that the colloidal silica composition of the present invention has a greater effect of promoting drainage and retention in the papermaking process by 20 to 40% as compared with the conventionally known composition. Furthermore, the composition of the present invention unexpectedly exhibited activity in a region where the conventionally known composition does not exhibit activity, that is, mainly in acidic paper stock (furnish) used in the papermaking process. A preferred application for the colloidal silica composition of the present invention is in facilitating drainage and retention in the papermaking process, but the composition of the present invention is used for other purposes such as beer, wine, juice, sugar refining; Use in water purification, including the production of water and wastewater; Use as a catalyst support; Use as a constituent of coating compositions; Coating components for plastics; Wear resistant coating components; Use in investment casting processes It can also be used as a constituent of a ceramic furnace material; and as a refractory material.

Accordingly, the present invention further includes a method of improving paper making, which method comprises adding the colloidal silica of the present invention to a paper mill stock to a slurry or dry weight of fibers in the stock. Of about 0.00005 to about 1.25% by weight based on the above amount. In another embodiment, the nonionic, cationic or anionic polymeric floc agent is added before or after the addition of colloidal silica from about 0.001 to about 0.001 based on the dry weight of the fibers in the stock. It may be added to the stock in an amount of 0.5% by weight. Alternatively, or instead of or in addition to the synthetic polymeric flocking agent, the cationic starch is added to about 0 based on the dry weight of the fibers in the stock.
． It may be added to the stock in an amount of 005 to about 5.0% by weight. More preferably, the starch is from about 0.05 to about 1.5% by weight, based on the dry weight of fiber in the stock.
Added in the amount of. In yet another embodiment, the flocculant, in place of or in addition to the polymeric flocking agent and / or starch, is about 0.005 to about 1.25 weight percent based on the dry weight of the fibers in the stock. %, May be added to the papermaking stock. Preferably, the flocculant is from about 0.025 to about 0, based on the dry weight of fibers in the stock.
． Add in an amount of 5% by weight.

The present invention also relates to a method for increasing retention and drainage of a papermaking stock on a paper machine, which method comprises adding the colloidal silica of the invention to a papermaking stock in a stock. About 0.00005 to about 1.25% by weight based on the dry weight of the fiber. The colloidal silica may be added to the papermaking stock together with the nonionic, cationic or anionic polymeric flocking agent. The polymeric flocking agent may be added before or after the colloidal silica from about 0.001 to about 0.5 wt% based on the dry weight of the fibers in the stock. Alternatively, starch may be added to the stock instead of or in addition to the polymeric flocking agent and added at about 0.005 to about 5.0% by weight based on the dry weight of the fibers in the stock. Is also good. If starch is used, cationic starch is preferred. At the time of its use, starch is preferably added in an amount of about 0.05 to about 1.25% by weight, based on the dry weight of the fibers in the stock. In yet another embodiment, the flocculant, instead of or in addition to the polymeric flocking agent and / or starch, is added to the flocculating agent at about 0.
It may be added to the papermaking stock in an amount of 005 to about 1.25% by weight. Preferably, the flocculant is added in an amount of about 0.025 to about 0.5% by weight, based on the dry weight of fibers in the stock.

In any of the above embodiments, the amount of the polymeric flocking agent used is preferably 0.005 to about 0.2 based on the dry weight of the fibers in the paper stock. The amount of colloidal silica used is from about 0.005 to about 0.005 based on the dry weight of the fibers in the stock.
It is preferably 25% by weight, and most preferably about 0.005 to about 0.15% by weight of the fibers in the stock.

It is pointed out that the above percentages may vary, as the present invention is applicable to a wide range of paper grades and stocks. It is within the spirit and intent of the present invention that the above percentages may be varied without departing from the invention.
These percentage values are only indicative to those skilled in the art.

In any of the above embodiments, bentonite, talc, synthetic clay, hectorite, kaolin, or a mixture thereof can be added at any stage of the papermaking system prior to sheet formation. The preferred point of addition is white water (wh
It is the time of high-concentration stock pulp before being diluted with (itewater). The use of this improved the cleanliness of the papermaking operation, and when it was not used, hydrophobic deposits were observed that affected both productivity and paper quality.

Further, in any of the above-mentioned modes, fine paper (when used in the text includes virgin fiber-based material as well as recycled fiber-based material), cardboard (when used in the text, virgin fiber-based material) Recycled fiber test liners and cardboard materials are included as well as materials), newsprint (when used in this text, magazine stock as well as virgin fiber and recycled fiber based materials), or It can be applied to a papermaking stock selected from the group consisting of other cellulosic materials. These stocks include wood-containing, non-wood-containing, virgin, bleached, unbleached, and mixtures thereof.

Papers and cardboards are generally made from suspensions of a stock of cellulosic material in an aqueous medium, the stock comprising one or more shearing steps (such as These steps are generally washing steps), followed by a mixing step and a pumping step, after which the suspension is dehydrated to form a sheet. Then this sheet
Dry to the desired (and generally low) water concentration. The colloidal silica of the present invention may be added to the stock before or after the shearing step.

In addition to its use in promoting retention and drainage as described above, the colloidal silica of the present invention may be used with standard cationic wet strength resins to provide wet strength of treated cellulose sheets. Improve. Colloidal silica, when used in such a manner, is pre-added to the stock prior to placing the stock containing the wet strength resin on the paper machine. Colloidal silica is commonly used at the levels listed above.

The colloidal silica of the present invention has been found to significantly improve the performance of synthetic polymeric floc agents, retention promoters and starch in the papermaking process. Further, colloidal silica is believed to have use as an additive in solid / liquid separation processes such as water pretreatment and in wastewater treatment applications. The colloidal silica of the present invention, in addition to improving drainage and retention in newsprint, high-quality paper, cardboard and other grades of paper, control of pitch and tackiness in papermaking, pulp dewatering in the production of dry lap pulp It may also find applications in pulp and paper mills for conserving and cleaning applications, clarification of water, degassing of dissolved air, dewatering of sludge, etc. The compositions of the present invention may also find use in solid / liquid separation and emulsion breaking.
Specific examples of such applications include dewatering sludge from municipal wastewater, clarification and dewatering of water-based inorganic slurries, and destruction of emulsions in refining equipment. Performance improvements seen by using the colloidal silica sols of the present invention in combination with synthetic polymers and / or starch include improved retention, improved drainage, and improved solid / liquid separation, and are often polymers. A reduction in the amount of starch and starch used is also recognized, and the desired effect can be achieved.

The particulate retention program is based on the recovery of flocs that originally formed but were destroyed by shear. In such applications, the flocking agent is added before the at least one high shear point and then the particulate is added just before the headbox. Typically, the flocking agent is added before the pressure screen, followed by the particulates after that screen. However, it was considered better to reverse the order of this method. The second flocs formed by the addition of fine particles have increased retention and drainage without adversely affecting sheet formation. This can increase the amount of filler in the sheet, prevent the two-sidedness of the sheet and increase drainage and paper machine speed in paper production.

The use of a slight excess of polymeric flocking agent and / or flocculant causes subsequent shearing to form microfloces fully loaded or loaded with the polymer and at least part of its surface is positively charged. It is considered necessary to ensure that all stock is not required to be positively charged. The zeta potential of the stock after addition of the polymer and after the shearing stage may be cationic or anionic.

Shearing may be performed by equipment within the equipment used for other purposes, such as mixing pumps, fan pumps, centriscreens, or for shear mixers or other purposes for shearing. Shearing stage may be inserted into the device, preferably a high degree of shearing is performed after polymer addition.

The flocking agent used in the application of the present invention is a high molecular weight water-soluble or water-dispersible polymer, which may have a cationic or anionic charge. A nonionic high molecular weight polymer may be used. These polymers may be those which are completely dissolved in the papermaking system, or those which are easily dispersed. They are so-called "silver dots" (fish eyes), which are often problematic.
It may have a branched or crosslinkable structure as long as no undissolved polymer mass is formed on the finished paper. Polymers belonging to these types are readily available from a variety of commercially available raw materials. They are dry solids, aqueous solutions,
A wate that can quickly dissolve the contained polymer when added to water
It is available as an r-in-oil type emulsion or as a polymer dispersible in a water-soluble dispersion medium or saline. It is believed that the high molecular weight floc form used herein is not limited to a particular polymer as long as it is a polymer that can be dissolved or dispersed in the stock.

As mentioned above, the polymer, whether cationic or anionic,
It may be nonionic. The cationic polymer flocking agent useful herein is generally a high molecular weight vinyl addition polymer incorporating a cationic functional group. These polymers are generally homopolymers of water-soluble cationic vinyl monomers or copolymers of water-soluble cationic vinyl monomers with nonionic monomers such as acrylamide and methacrylamide. It may be. The polymer may contain only one type of cationic vinyl monomer or may contain more than one type of cationic vinyl monomer. Alternatively, after polymerization, certain polymers such as polyacrylamide may be modified or derivatized by the Mannich reaction to produce the cationic vinyl polymers useful in the present invention. The polymer may be prepared from a small amount of the cationic monomer of about 1 mol% to 100 mol% of the cationic monomer,
It may be prepared from a cationically modified functional group on the polymer modified after the polymerization. The most frequently used cationic floc agents will be those with 5 mol% or more of cationic vinyl monomers or functional groups. And most preferably 1
It will have 0% by weight or more of a cationic vinyl monomer or functional group.

Suitable cationic vinyl monomers that can be used to prepare the cationically charged vinyl-based addition copolymers and homopolymers suitable for the present invention are well known to those skilled in the art. Ah These materials include dimethylaminoethylmethacrylate (DMAEM), dimethylaminoethylacrylate (DMA)
EA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM), or their quaternary ammonium compounds formed using dimethylsulfate or methyl chloride, polyacrylamide modified by Mannich reaction, diallylcyclohexylamine hydrochloride ( DACHA HCl), diallyldimethylammonium hydrochloride (DADMAC), methacrylamidopropyltrimethylammonium hydrochloride (MAPTAC), and allylamine (ALA). Cationized starch may also be used herein as a flocking agent. The flocking agent selected may be a mixture of the above or it may be a mixture of the above and a cationic starch. Those skilled in the art of cationic polymer-based retention programs will find that the selection of a particular polymer is limited to stock, filler, grade,
And you will easily recognize that it depends on water quality.

The high molecular weight anionic flocculant useful in the present invention is preferably a water-soluble or water-dispersible vinyl-based polymer containing 1 mol% or more of a monomer having an anionic charge. Thus, these polymers may be homopolymers of water-soluble anionic charged vinyl monomers, or copolymers of these monomers with nonionic monomers such as acrylamide and methacrylamide. It may be. Specific examples of suitable anionic monomers include acrylic acid, methacrylamide, 2-acrylamido-2-methylpropane sulfonate (
AMPS) and mixtures thereof, as well as their corresponding water-soluble or water-dispersible alkali metal and ammonium salts. The anionic high molecular weight polymer useful in the present invention may be a hydrolyzate of an acrylamide polymer, or acrylamide or its homologues such as methacrylamide and acrylic acid or its homologues such as methacrylic acid. ) Or with copolymers of polymers of vinyl monomers such as maleic acid, itaconic acid, vinyl sulphonic acid or other sulphonate containing monomers. The anionic polymer may have a sulfonate or phosphonate functional group and may be prepared by derivatizing a polymer or copolymer of polyacrylamide or polymethacrylamide. The most preferred high molecular weight anionic flocculants are acrylic acid / acrylamide copolymers and 2-acrylamido-2-methylpropane sulfonate, acrylamidomethanesulfonate, acrylamidoethanesulfonate and 2-hydroxy-3-acrylamidopropanesulfonate. Sulfonate-containing polymers as prepared by polymerizing monomers such as acrylamide with other nonionic vinyl monomers. As used herein, the anionic vinyl monomer polymer or copolymer may contain a small amount of anionic charged monomer such as about 1 mol%, and preferably contains 10 mol% or more of anionic monomer. . Again, the choice to use a particular anionic polymer will depend on the stock, filler, water quality, paper grade, etc.

Although most fine particle programs perform well only with high molecular weight cationic flocking agents, the colloidal silica sols of the present invention may be used with high molecular weight anionic water-soluble flocking agents or with cationic It may be used together with the addition of a coagulant.

The nonionic floc agent useful in the present invention may be selected from the group consisting of polyethylene oxide and poly (meth) acrylamide. In addition to the above, in certain cases it is advantageous to use so-called amphoteric water-soluble polymers. These polymers carry both cationic and anionic charges in the same polymer chain.

The nonionic, cationic, anionic vinyl polymer flocking agents useful herein generally have a molecular weight of 500,000 daltons or more, preferably 1,000,000 daltons or more. Will. The water-soluble or water-dispersible flocking agents useful herein may have a molecular weight of 5,000,000 or higher, for example in the range of 10,000,000 to 30,000,000,
Or more. Polymers suitable for the present invention may be completely water-soluble when applied to the system or may be slightly branched (two-dimensional), as long as the polymer is water dispersible It may be crosslinked (three-dimensional). Although it is preferred to use completely water-soluble polymers, dispersible polymers as described in WO 97/16598 may be employed. Useful polymers are available from Langley et.
It may be substantially linear in the meaning as defined in Al., U.S. Pat. No. 4,753,710. The upper limit of molecular weight is governed by the solubility or dispersibility of the product in the papermaking stock.

Cationic or amphoteric starches useful in the application of the present invention are generally described in US Pat. No. 4,385,961, the disclosure of which is incorporated herein by reference. Be done. Cationic starch materials are generally guar gum (gu
selected from the group consisting of naturally occurring polymers based on carbohydrates such as ar gum) and starch. Cationic starch materials that are considered to be most useful in practice for the present invention include starch materials derived from wheat, potato and rice. These materials may be sequentially reacted to substitute an ammonium group on the starch skeleton, and Dondeyne
It may be cationized according to the method shown by et al in WO 96/30591. Generally, starches useful in the present invention have a degree of substitution (ds) of ammonium groups within the starch molecule of between about 0.01 and 0.05. This degree of substitution is based on basic starch, ether 3-chloro-2-hydroxypropyl-trimethylammonium chloride, or 2,3-epoxypropyl-trimethylammonium chloride.
Obtained by reacting chloride, cationized starch is obtained. As will be appreciated, means for cationizing starch materials are beyond the scope and intent of the present invention, and these modified starch materials are well known and readily available from a variety of commercial sources. .

Various characteristics of cellulosic stocks, such as pH, hardness, ionic strength, and cation requirements affect the performance of the flocking agent in the proposed application. The choice of flocking agent takes into account the type of charge, the charge density, the molecular weight, and the type of monomer, and depends in particular on the water and the chemistry of the stock to be treated.

Other additives may be loaded into the cellulosic paper stock without substantially interfering with the activity of the present invention. Such other additives include, for example, sizing agents such as alum and rosin, pitch control agents, extenders, biocides and the like. The cellulosic paper stock to which the retention promoting program of the present invention is added may contain pigments and / or fillers such as titanium dioxide, precipitated and / or ground calcium carbonate and other inorganic or organic fillers. The present invention can be combined with other so-called particulate programs, such as bentonite and kaolin, and are within the spirit of the invention. When the paper producer changes grades and stocks, the combination of the colloidal silica sol of the invention with other particulates is practically possible and preferred under certain circumstances.

The colloidal silica sols of the present invention are described in Sofia et al., US Pat. No. 4,795,5.
It may also be used in combination with a flocculant according to the teachings of No. 31, the disclosure of which is incorporated herein by reference. Sofia teaches a microparticle program that uses microparticles in the presence of a cationic flocculant and a high molecular weight charged floc agent.

Cationic flocculant materials that can be used in this form of the invention include the well-known commercially available low to medium molecular weight water-soluble polyalkylene polyamines, which are alkylene polyamines with difunctional alkyls. Those prepared by reacting with a halide are applicable. This type of material is prepared from the reaction of ethylene dichloride with ammonia or the reaction of ethylene dichloride with ammonia with secondary amines (dimethylamine, epichlorohydrin-dimethylamine, epichlorohydrin-dimethylamine-ammonia, polyethyleneimine, etc.) Includes condensation polymer polymers. In addition, diallyldimethylammonium halide (particularly diallyldimethylammonium chloride), dialkylaminoalkyl acrylate,
Also useful are high molecular weight solution polymerized and copolymerized polymers of vinyl monomers such as quaternary ammonium salts of dialkylaminoalkyl acrylates and the like.
Here, the “alkyl” has 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms.
Represents the group of. Preferably "alkyl" is methyl. Examples of these monomers include materials such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and water-soluble quaternary ammonium salts thereof. In certain cases, cationic starch may be used as a flocculant. Inorganic flocculants such as alum and polyaluminum chloride may be used in the present invention. The amount of the inorganic flocculant used is typically 0.05 to 2% by weight based on the dry weight of the fibers in the stock. The use of a flocculant in combination with the colloidal silica sol is optional.

The method of the present invention is applicable to all grades and types of paper products containing the fillers described herein, and further includes chemical pulp (sulfate pulp, sulfite pulp obtained from both hardwood and softwood). ), Thermo-mechanical pulp, mechanical pulp, groundwood pulp and the like, and is applicable when using all types of pulp, and the type of pulp is not limited.

In the papermaking process, the inorganic filler is generally added to the papermaking raw material and used in an amount of about 10 to about 30 parts by weight of filler per 100 parts by weight of dry fiber in the paper stock. However, the amount of such fillers may sometimes be as low as about 5 parts by weight or 0 parts by weight, and as high as about 40 parts by weight or 50 parts by weight, on the same basis.

The following examples serve to illustrate the invention and should not be construed in a limiting way.

Example 1 Preparation of Colloidal Silica Sol of the Invention 285.8 pounds of soft water was charged to a reactor equipped with a recirculation pump and recirculated at a rate of 50 gallons per minute (gpm). To start. 5.63 lbs of 95 wt% sulfuric acid solution is added slowly to the reactor, cooling the reactor contents as needed to cool below 75 ° F. After circulating the reactor contents for 5 minutes, 289.5 lbs of sodium silicate having a SiO _{2 to} Na ₂ O molar ratio of 3.26 and a pH of 11.2 is added. Cooling is performed so that the reactor temperature does not exceed 81 ° F. The addition of aqueous silicic acid was started after the addition of sodium silicate,
Pounds of the aqueous silicic acid (SiO ₂ solid content is 6.40% by weight), at a rate of 13.20 lbs / minute (or 1.52 gallons / minute), is added while maintaining the temperature at 80 ° F . When filled with 75% silicic acid (2376.8 lbs) (approximately 3.
At 0 hours) slowly ramp up at a rate of 0.7 ° F / min until the temperature reaches 120 ° F. Continue to add silicic acid while heating the composition. The composition temperature is 100
The time required to reach ° F is 10 minutes and the elapsed time to reach 115 ° F is 36 minutes. After all the silicic acid has been added, maintain the temperature of the composition at 120 ° F. for 1 hour (ie, start timing after the silicic acid addition is complete). The temperature is then maintained at 118-122 ° F and the composition is ultrafiltered to increase the solids concentration of the composition. When the silica concentration reaches 14.8 to 16.6 wt%, preferably 15.0 wt%, ultrafiltration is stopped.

The resulting colloidal silica composition of the present invention was determined to have a specific gravity of 1.1048, a silica surface area of 804.3 m ² / g, and an S-value of 48.1. After a further 45 days at room temperature, the surface area of the silica was determined to be 751 m ² / g.

Example 2 151.2 g of deionized water and 4.0 g of sodium sulfate are charged to a round bottom flask and stirred until the sodium sulfate is dissolved. 124.8 g with mixing
Of sodium silicate is added to the flask. Heat the contents of the flask to 80 ° F. A total of 1720 g silicic acid (specific gravity 1.039) is added to the flask at a rate of 7.2 g / min over 4 hours. The contents of the flask are heated to a final temperature of 120 ° F after the addition of 860g or 1/2 of silicic acid. Continue to add silicic acid while heating the composition. Thereafter, the temperature is maintained at 118-122 ° F. After the fourth hour final addition, the reaction flask is cooled to room temperature and 350 g of the composition is ultrafiltered to increase the solids concentration of the composition. Ultrafiltration is stopped when the measured amount of water removed reaches 166.82 g. The solids content of the final composition is 16.12% by weight.

The resulting colloidal silica composition of the present invention was determined to have a specific gravity of 1.1067, a silica surface area of 904 m ² / g and an S-value of 39. 33 more days later,
The surface area of silica was measured to be 904 m ² / g.

Example 3 Preparation of the Colloidal Silica Sol of the Invention 285 pounds of soft water is charged to a reactor equipped with a recirculation pump and recirculation is initiated at a rate of 50 gpm. 5.63 lbs of 95 wt% sulfuric acid solution is added slowly to the reactor, cooling the reactor contents as needed to cool below 75 ° F. After circulating the reactor contents for 5 minutes, the Si to Na ₂ O
Add 290 lbs of sodium silicate with an O ₂ molar ratio of 3.26 and a pH of 11.2. Cooling is performed so that the reactor temperature does not exceed 81 ° F. Sodium silicate addition of aqueous silicate started after the addition, 3,225 lbs of aqueous silicic acid (SiO ₂ solids 6.37% by weight, a viscosity of 2.9 centipoise, a specific gravity of 1.0388 and, pH
Is 2.76) at a rate of 13.4 lbs / min while maintaining the temperature at 80 ° F. When filled with 75% silicic acid (2419 lbs) (approximately 3
． At 0 hours) slowly ramp up at a rate of 0.7 ° F / min until the temperature reaches 120 ° F. Continue to add silicic acid while heating the composition. The temperature of the composition is 10
The time required to reach 0 ° F is 40 minutes, and the elapsed time to reach 115 ° F is 57 minutes. After all the silicic acid has been added, the composition temperature is 120 ° F.
For 1 hour (ie, start timing after silicic acid addition is complete). The temperature is then maintained at 118-122 ° F and the composition is ultrafiltered to increase the solids concentration of the composition. Silica concentration of 14.8 to 16.6% by weight,
Ultrafiltration is stopped, preferably when it reaches 15.0% by weight.

The resulting colloidal silica composition of the present invention was determined to have a specific gravity of 1.1033, a silica surface area of 786.4 m ² / g, and an S-value of 41. The surface area after 51 days was measured to be 711.2 m ² / g.

Example 4 (Preparation of the Colloidal Silica Sol of the Present Invention) A sodium Amberlite ™ IRC84SP ion exchange resin (available from Rohm & Haas) was placed in a reactor equipped with a screen near the bottom of the tank. ) For 226 gallons. In order to regenerate the resin to the hydrogen form with 40% or more complete regeneration, follow the manufacturer's defined procedure. Rinse resin thoroughly with water and drain.

Fill the reactor with 1469 pounds of water, start mixing the contents of the reactor, and suspend the resin. The reactor contents are then heated to 75 ° F. 1231 lbs of silicic acid diluted with 564 lbs of water (SiO _{2 to} Na ₂ O molar ratio 3.26).
And the pH is 11.2) is charged to the reaction tank (filling for 10 minutes).
. The pH and electrical conductivity of the contents of the reactor are monitored about every 10 minutes until the pH reaches 9.8 and the electrical conductivity reaches 5800 μmho. To the contents of the reactor was added 150 pounds of sodium silicate (as described above) and the pH was about 10.
Raise to 6. The contents of the vessel were stirred for about 20 minutes, after which the contents of the reactor were removed from the bottom through a screen. A small amount of water was passed through the resin and washed with water to remove the residual product, which was mixed with the product.

The resulting colloidal silica composition of the present invention has a specific gravity of 1.0877, a silica surface area of 927.4 m ² / g, an S-value of 32, and a SiO ₂ solids content of 1% by weight.
It was determined to be 2.9%.

Example 5 A. Preparation of Synthetic Standard Stock-Alkaline stock-The alkaline stock has a pH of 8.1, 70% by weight of cellulose fibers and 30% by weight.
The total concentration of the synthetic formulation water (synthetic formulation wa
ter) and diluted to 0.5% by weight. Cellulose fiber is 60% by weight
Bleached hardwood kraft and 40% by weight bleached softwood kraft. Each of these was struck with a dry wrap to produce Canadian Standard Freeness (Cana
It was prepared so that the value of dian Standard Freeness (CSF) is in the range of 340 to 380. The filler was commercially available ground calcium carbonate, which was a dried product. Formulated water has a calcium hardness of 200 ppm (added as CaCl ₂ ),
152 ppm magnesium hardness (added as MgSO ₄ ) and 110 ppm
Of bicarbonate alkalinity (added as NaHCO ₃ ).

Acidic Stock-The acidic stock consisted of kraft with a hardwood / softwood weight ratio of 60/40. As mentioned above, the fibers should be pre-mixed before being mixed with the filler and water.
0 to 380 CSF respectively. The total solids of the stock consists of 92.5% by weight cellulose fibers and 7.5% by weight filler. For the filler, 2.
5 wt% titanium dioxide (Titanox from DuPont) and 5.0 wt% kaolin clay were mixed. The water used to dilute the fibers and fillers also contains additional salts as outlined in the alkaline stock above.
Other additives included alum in an amount to provide 20 lbs activity per ton of dry solids. The pH of the stock was adjusted with 50% diluted sulfuric acid so that the pH of the stock after addition of alum was 5.0.

FBRM Data (Measurement of Focused Beam Reflectance) Scanning laser microscopy performed in the following examples is described in US Pat. No. 4,871,
251 (issued to Preikschat, FK and E. (1989)),
Generally, it is composed of a laser source, an optical system for supplying irradiation light and collecting scattered light from the paper stock, a photodiode, and a signal analysis device. Commercially available equipment is available from Lasentec, Redmond, Washington.

The experiment takes 300 mL of a cellulosic fiber containing slurry and places it in a suitable mixing beaker. Shear the stock with a variable speed motor and propeller. The mixer is set at 720 rpm for all experiments here. The propeller was installed at a fixed distance from the probe window to ensure movement of the slurry across the window. For both alkaline and acidic stocks,
A typical test procedure is shown below.

[0055]

[Table 1]

[0056]

[Table 2]

The change in the average chord length of the flocs after addition of fine particles was evaluated for correlation with the dynamic drainage jar (Jar) retention measurement. As a result, the greater the change in average chord length change induced by the process, the higher the hold value.

Physical Properties of Test Materials The following materials are used in the examples of this patent, but their physical properties are specified below.

[0059]

[Table 3]

B (1). Improving Acid Stock Retention Synthetic acid stock was prepared as outlined above in "Standard Synthetic Stock". F
The following results were obtained by the BRM experiment.

[0061]

[Table 4]

As can be seen from the above data, the material which is the subject of the present invention shows an improvement of approximately 60-70% at an activity level of 2 lbs / ton, increasing the degree of flocculation in this synthetic acid stock. It was B (2). Improving retention of alkaline stock The material was tested for "standard alkaline synthetic stock" in a similar manner.
The FBRM experiment was also performed, and the results are summarized as follows.

[0063]

[Table 5]

The above results show that the material produced by the method here has a higher retention in alkaline paper stock than conventional colloidal silica. In this case, the improvement rate is from 50% of the conventional colloidal silica to more than 100%.

In yet another experiment conducted with the above-mentioned alkaline paper stock, the following results were observed.

[0066]

[Table 6]

In the above experiments, the material which is the subject of the present invention improved the degree of flocking in synthetic alkaline stocks by more than 100% compared to conventional colloidal silica. As a result, the material according to the present invention provided a significant improvement effect on the retention of the alkaline stock. C. Improvement of drainage The drainage was measured using a vacuum drainage tester (Narco Chemical Co.). 500 m
A raw material of L capacity was put into a raw material storage tank of the equipment, supplied with an additive while stirring, and drained. The drainage of the raw material is done under vacuum, in this case Filpaco # 716 (Filp
ako # 716) Made on a cellulose filter. The time required from the start of drainage until the air was drawn through the pad was recorded as the "drainage time". The final vacuum value read from the vacuum gauge was recorded 10 seconds after the vacuum was terminated. The added vacuum level is 14 in. In Hg. , The mixing speed was 900 rpm, and the digital Cole-Palmer Servo Dyne mixer system controller (digital Cole-Palme
r ServoDyne Mixer System Controller).

The stock used in this test was 13% softwood, 49.4% hardwood and 6% ground wood.
． It is an alkaline stock composed of 0% and 31.6% of broke. Starch (staloc cationic starch) was added at 40 lbs / ton. Flock agent is 10
It consisted of mol% cationic polyacrylamide (cPAM). It was added at 0.6 lbs / ton. The procedure of addition is as follows.

[0069]

[Table 7]

The drainage time, final vacuum, and drainage rate (defined as the time required to drain 300 mL of filtration) were also recorded. The results are summarized in the table below.

[0071]

[Table 8]

As can be seen from this data, the material that is the subject of this patent, namely Sample 4
Increased the drainage rate by a factor of 7 compared to the blank and by a factor of 2 compared to the single treatment with the floc agent. Similar enhancement effects were observed for drainage rate and final vacuum. Therefore, the material which is the subject of the present invention improves drainage.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, SD, SL, SZ, UG, ZW), E A (AM, AZ, BY, KG, KZ, MD, RU, TJ , TM), AE, AL, AM, AT, AU, AZ, BA , BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, G E, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, M N, MW, MX, NO, NZ, PL, PT, RO, RU , SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZA, Z W (72) Inventor Kaiser, Bruce, A.             Na, United States, 60565, Illinois             Paville, Breckenridge Rain             2708 (72) Inventor Nan, Maureen, Bee.             Na, United States, 60565, Illinois             Paville, Newport Drive 2648 (72) Inventor Huan, Chen Sun             Na, United States, 60565, Illinois             Paville, Morgan Circle 1876 (72) Inventor McDonald, Dennis, Elle.             United States, 60187, Illinois, Ho             Eaton, Hampton Drive 1914 F-term (reference) 4G072 AA28 CC04 EE01 HH21 JJ13                       MM14 PP11 TT05 UU25                 4L055 AA02 AA03 AC06 AG18 AG48                       AG73 AH01 AH18 EA17 EA20                       EA25 EA30 EA31 EA32 EA40                       FA10

Claims (23)

[Claims] 1. A stable colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50. 2. The colloidal silica according to claim 1, wherein the surface area is 750 m ² / g or more. 3. The colloidal silica according to claim 1, wherein the surface area is 800 m ² / g or more. 4. The colloidal silica of claim 1, wherein said S-value is 40 or less than 40. 5. The colloidal silica according to claim 1, which has a solids weight% based on SiO ₂ of 7% or more. 6. The colloidal silica of claim 5 having a solids weight percent based on SiO ₂ of 10 to 20%. 7. A process for preparing stable colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50: (a) water and the moles of SiO ₂ with respect to the alkali metal oxide. A ratio of 15: 1 to 1: 1 and a pH of 10 or more alkali metal silicate, and a compound selected from the group consisting of an acid, a salt corresponding to the acid, and a mixture thereof. Prepares a starting composition in which the alkali metal silicate salt and the compound are present in a weight ratio of 63: 1 or more, and maintains the temperature of the starting composition at 90 ° F or lower; (b) An aqueous silicic acid composition having an amount of SiO ₂ of 4.0 to 8.5% by weight and a temperature maintained at 90 ° F. or lower was slowly and continuously added to the starting composition for 2 minutes of the silicic acid composition. Adding from 1 to 3/4; (c) said The composition is slowly warmed to 115-125 ° F and maintained at that temperature until the addition of the silicic acid composition is complete; (d) optionally, the composition at 125 ° F or less for about 1 hour. Maintain; (e) stop heating and optionally 7% by weight solids based on SiO _2.
A method for preparing stable colloidal silica, characterized in that water is removed from the composition until the above. 8. The method of claim 7, wherein in step (b) the temperature is maintained in the range of 60 to 90 ° F. 9. The method of claim 7, wherein in step (d) the temperature is maintained in the range of 115-125 ° F. 10. The method of claim 7, wherein in step (e), water is removed from the composition until the solid content is 10% by weight or more. 11. A method for preparing stable colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50: (a) The reaction vessel has an ion exchange capacity in hydrogen form. 40% or more of a cation exchange resin is filled, and the reaction tank has means for separating the colloidal silica from the ion exchange resin; (b) The reaction tank contains SiO ₂ with respect to an alkali metal oxide. Molar ratio of 15
1 to 1: 1 and a pH of 10.0 or more is filled with an aqueous alkali metal silicate; (c) The content of the reaction vessel is adjusted to pH 8.5 to 11. Stir until it reaches the range of 0; (d) Add the alkali metal silicate and adjust the pH of the contents of the reaction vessel to 1;
Adjusted to 0.0 or more; (e) A method for preparing stable colloidal silica, characterized in that the produced colloidal silica is separated from the ion exchange resin and taken out from the reaction tank. 12. The method of claim 11, wherein the means for separating the colloidal silica from the ion exchange resin comprises a screen provided near the bottom of the reaction vessel. 13. In step (c), the pH of the contents is 9.2 to 10.
． The method of claim 11, wherein 0. 14. The method according to claim 11, wherein in step (a), the molar ratio of hydrogen ions in the cation exchange resin to alkali metal ions in the alkali metal silicate is in the range of 40 to 100%. 15. In the step (c), the content of the reaction vessel is 50 to 10
12. The method of claim 11 maintained at 0 ° F. 16. In step (c), the pH of the contents is 9.2 to 10.
． The method of claim 11 in the range of 5. 17. In step (d), the pH of the contents of the reaction vessel is adjusted to 10.
The method according to claim 11, wherein the method is adjusted to 4 to 10.7. 18. A method of making a cellulose sheet, comprising: a. Preparing a cellulose stock containing 0.01 to 1.5% by weight of cellulose fibers; b. For the stock, (i) stable colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50 is added to about 0 based on the dry weight of the fibers in the stock. .00
005 to about 1.25% by weight; and (ii) a substantially water-soluble polymeric flocking agent having a molecular weight of 500,000 daltons or more and about 0.001 based on the dry weight of the fibers in the stock. To about 0.
5% by weight; c. A method for producing a cellulose sheet, which comprises dehydrating the paper material to obtain a cellulose sheet. 19. The method of claim 18, further comprising the additional step of adding a cationic flocculant to the stock before adding the polymeric flocking agent to the stock. 20. A method of making a cellulose sheet, comprising: a. Preparing a cellulose stock containing 0.01 to 1.5% by weight of cellulose fibers; b. For the stock, (i) stable colloidal silica having a surface area of 700 m ² / g or more and an S-value of 20 to 50 is added to about 0 based on the dry weight of the fibers in the stock. .00
005 to about 1.25% by weight; and (ii) the cationic starch, about 0, based on the dry weight of the fibers in the stock.
． 005 to about 5.0% by weight; c. A method for producing a cellulose sheet, which comprises dehydrating the paper material to obtain a cellulose sheet. 21. A substantially water-soluble polymeric flocking agent having a molecular weight of 500,000 daltons or more is added to the paper stock in an amount of about 0.001 to about 1 to 100, based on the dry weight of the fibers in the paper stock. 21. The method of claim 20, further comprising step b (iii) adding about 0.5% by weight. 22. A method for increasing the drainage of a stock made on a paper machine, comprising: 700 m ² / g or more of the stock to be made before placing it on the paper machine. Stable colloidal silica having a surface area of 20 to 50 and an S-value of 20 to 50, based on the dry weight of the fibers in the stock, from about 0.00005 to about 1.25% by weight,
And a polymer flocculant in an amount of about 0.00 based on the dry weight of the fibers in the stock.
A method of increasing the drainage rate from the stock on the paper machine by adding 1 to about 0.5% by weight; placing the stock on a paper machine; and bringing the stock into a papermaking state. 23. Prior to placing the stock to be papermaking on a paper machine, a cationic starch is further added to the stock to about 0.0, based on the dry weight of the fibers in the stock.
23. The method of claim 22, wherein the amount added is from 05 to about 5.0% by weight.